﻿using UnityEngine;
using UnityEditor;
using System.Collections;
using System.IO;
using System.Text;

public class ObjExporterScript
{
    private static int StartIndex = 0;

    public static void Start()
    {
        StartIndex = 0;
    }
    public static void End()
    {
        StartIndex = 0;
    }


    public static string MeshToString(MeshFilter mf, Transform t) 
    {   
        Vector3 s       = t.localScale;
        Vector3 p       = t.localPosition;
        Quaternion r    = t.localRotation;


        int numVertices = 0;
        Mesh m = mf.sharedMesh;
        if (!m)
        {
            return "####Error####";
        }
        Material[] mats = mf.GetComponent<Renderer>().sharedMaterials;

        StringBuilder sb = new StringBuilder();

        foreach(Vector3 vv in m.vertices)
        {
            Vector3 v = t.TransformPoint(vv);
            numVertices++;
            sb.Append(string.Format("v {0} {1} {2}\n",v.x,v.y,-v.z));
        }
        sb.Append("\n");
        foreach(Vector3 nn in m.normals) 
        {
            Vector3 v = r * nn;
            sb.Append(string.Format("vn {0} {1} {2}\n",-v.x,-v.y,v.z));
        }
        sb.Append("\n");
        foreach(Vector3 v in m.uv) 
        {
            sb.Append(string.Format("vt {0} {1}\n",v.x,v.y));
        }
        for (int material=0; material < m.subMeshCount; material ++) 
        {
            sb.Append("\n");
            sb.Append("usemtl ").Append(mats[material].name).Append("\n");
            sb.Append("usemap ").Append(mats[material].name).Append("\n");

            int[] triangles = m.GetTriangles(material);
            for (int i=0;i<triangles.Length;i+=3) {
                sb.Append(string.Format("f {0}/{0}/{0} {1}/{1}/{1} {2}/{2}/{2}\n", 
                    triangles[i]+1+StartIndex, triangles[i+1]+1+StartIndex, triangles[i+2]+1+StartIndex));
            }
        }

        StartIndex += numVertices;
        return sb.ToString();
    }
}

public class ObjExporter : ScriptableObject
{
    [MenuItem ("File/Export/Wavefront OBJ")]
    static void DoExportWSubmeshes()
    {
        DoExport(true);
    }

    [MenuItem ("File/Export/Wavefront OBJ (No Submeshes)")]
    static void DoExportWOSubmeshes()
    {
        DoExport(false);
    }


    static void DoExport(bool makeSubmeshes)
    {
        if (Selection.gameObjects.Length == 0)
        {
            Debug.Log("Didn't Export Any Meshes; Nothing was selected!");
            return;
        }

        string meshName = Selection.gameObjects[0].name;
        string fileName = EditorUtility.SaveFilePanel("Export .obj file", "", meshName, "obj");

        ObjExporterScript.Start();

        StringBuilder meshString = new StringBuilder();

        meshString.Append("#" + meshName + ".obj"
            + "\n#" + System.DateTime.Now.ToLongDateString() 
            + "\n#" + System.DateTime.Now.ToLongTimeString()
            + "\n#-------" 
            + "\n\n");

        Transform t = Selection.gameObjects[0].transform;

        Vector3 originalPosition = t.position;
        t.position = Vector3.zero;

        if (!makeSubmeshes)
        {
            meshString.Append("g ").Append(t.name).Append("\n");
        }
        meshString.Append(processTransform(t, makeSubmeshes));

        WriteToFile(meshString.ToString(),fileName);

        t.position = originalPosition;

        ObjExporterScript.End();
        Debug.Log("Exported Mesh: " + fileName);
    }

    static string processTransform(Transform t, bool makeSubmeshes)
    {
        StringBuilder meshString = new StringBuilder();

        meshString.Append("#" + t.name
            + "\n#-------" 
            + "\n");

        if (makeSubmeshes)
        {
            meshString.Append("g ").Append(t.name).Append("\n");
        }

        MeshFilter mf = t.GetComponent<MeshFilter>();
        if (mf)
        {
            meshString.Append(ObjExporterScript.MeshToString(mf, t));
        }

        for(int i = 0; i < t.childCount; i++)
        {
            meshString.Append(processTransform(t.GetChild(i), makeSubmeshes));
        }

        return meshString.ToString();
    }

    static void WriteToFile(string s, string filename)
    {
        using (StreamWriter sw = new StreamWriter(filename)) 
        {
            sw.Write(s);
        }
    }
}
